TY - JOUR A1 - Wolter, Juliane A1 - Lantuit, Hugues A1 - Herzschuh, Ulrike A1 - Stettner, Samuel A1 - Fritz, Michael T1 - Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries JF - The Holocene : an interdisciplinary journal focusing on recent environmental change KW - pollen Y1 - 2017 U6 - https://doi.org/10.1177/0959683617708441 SN - 0959-6836 SN - 1477-0911 VL - 27 SP - 1846 EP - 1858 PB - Sage Publ. CY - London ER - TY - JOUR A1 - Wischnewski, Juliane A1 - Kramer, Annette A1 - Kong, Zhaochen A1 - Mackay, Anson W. A1 - Simpson, Gavin L. A1 - Mischke, Steffen A1 - Herzschuh, Ulrike T1 - Terrestrial and aquatic responses to climate change and human impact on the southeastern Tibetan Plateau during the past two centuries JF - Global change biology N2 - Rapid population growth and economic development have led to increased anthropogenic pressures on the Tibetan Plateau, causing significant land cover changes with potentially severe ecological consequences. To assess whether or not these pressures are also affecting the remote montane-boreal lakes on the SE Tibetan Plateau, fossil pollen and diatom data from two lakes were synthesized. The interplay of aquatic and terrestrial ecosystem response was explored in respect to climate variability and human activity over the past 200 years. Nonmetric multidimensional scaling and Procrustes rotation analysis were undertaken to determine whether pollen and diatom responses in each lake were similar and synchronous. Detrended canonical correspondence analysis was used to develop quantitative estimates of compositional species turnover. Despite instrumental evidence of significant climatic warming on the southeastern Plateau, the pollen and diatom records indicate very stable species composition throughout their profiles and show only very subtle responses to environmental changes over the past 200 years. The compositional species turnover (0.36-0.94 SD) is relatively low in comparison to the species reorganizations known from the periods during the mid-and early-Holocene (0.64-1.61 SD) on the SE Plateau, and also in comparison to turnover rates of sediment records from climate-sensitive regions in the circum arctic. Our results indicate that climatically induced ecological thresholds are not yet crossed, but that human activity has an increasing influence, particularly on the terrestrial ecosystem in our study area. Synergistic processes of post-Little Ice Age warming, 20th century climate warming and extensive reforestations since the 19th century have initiated a change from natural oak-pine forests to seminatural, likely less resilient pine-oak forests. Further warming and anthropogenic disturbances would possibly exceed the ecological threshold of these ecosystems and lead to severe ecological consequences. KW - climate change KW - compositional species turnover KW - diatoms KW - human impact KW - pollen KW - Procrustes rotation KW - Tibetan Plateau Y1 - 2011 U6 - https://doi.org/10.1111/j.1365-2486.2011.02474.x SN - 1354-1013 VL - 17 IS - 11 SP - 3376 EP - 3391 PB - Wiley-Blackwell CY - Malden ER - TY - GEN A1 - Tian, Fang A1 - Herzschuh, Ulrike A1 - Mischke, Steffen A1 - Schlütz, Frank T1 - What drives the recent intensified vegetation degradation in Mongolia BT - Climate change or human activity? T2 - The Holocene N2 - This study examines the course and driving forces of recent vegetation change in the Mongolian steppe. A sediment core covering the last 55years from a small closed-basin lake in central Mongolia was analyzed for its multi-proxy record at annual resolution. Pollen analysis shows that highest abundances of planted Poaceae and highest vegetation diversity occurred during 1977-1992, reflecting agricultural development in the lake area. A decrease in diversity and an increase in Artemisia abundance after 1992 indicate enhanced vegetation degradation in recent times, most probably because of overgrazing and farmland abandonment. Human impact is the main factor for the vegetation degradation within the past decades as revealed by a series of redundancy analyses, while climate change and soil erosion play subordinate roles. High Pediastrum (a green algae) influx, high atomic total organic carbon/total nitrogen (TOC/TN) ratios, abundant coarse detrital grains, and the decrease of C-13(org) and N-15 since about 1977 but particularly after 1992 indicate that abundant terrestrial organic matter and nutrients were transported into the lake and caused lake eutrophication, presumably because of intensified land use. Thus, we infer that the transition to a market economy in Mongolia since the early 1990s not only caused dramatic vegetation degradation but also affected the lake ecosystem through anthropogenic changes in the catchment area. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 418 KW - central Mongolia KW - grain size KW - human impact KW - lake eutrophication KW - pollen KW - vegetation degradation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-404201 ER - TY - JOUR A1 - Tian, Fang A1 - Herzschuh, Ulrike A1 - Mischke, Steffen A1 - Schluetz, Frank T1 - What drives the recent intensified vegetation degradation in Mongolia - Climate change or human activity? JF - The Holocene : an interdisciplinary journal focusing on recent environmental change N2 - This study examines the course and driving forces of recent vegetation change in the Mongolian steppe. A sediment core covering the last 55years from a small closed-basin lake in central Mongolia was analyzed for its multi-proxy record at annual resolution. Pollen analysis shows that highest abundances of planted Poaceae and highest vegetation diversity occurred during 1977-1992, reflecting agricultural development in the lake area. A decrease in diversity and an increase in Artemisia abundance after 1992 indicate enhanced vegetation degradation in recent times, most probably because of overgrazing and farmland abandonment. Human impact is the main factor for the vegetation degradation within the past decades as revealed by a series of redundancy analyses, while climate change and soil erosion play subordinate roles. High Pediastrum (a green algae) influx, high atomic total organic carbon/total nitrogen (TOC/TN) ratios, abundant coarse detrital grains, and the decrease of C-13(org) and N-15 since about 1977 but particularly after 1992 indicate that abundant terrestrial organic matter and nutrients were transported into the lake and caused lake eutrophication, presumably because of intensified land use. Thus, we infer that the transition to a market economy in Mongolia since the early 1990s not only caused dramatic vegetation degradation but also affected the lake ecosystem through anthropogenic changes in the catchment area. KW - central Mongolia KW - grain size KW - human impact KW - lake eutrophication KW - pollen KW - vegetation degradation Y1 - 2014 U6 - https://doi.org/10.1177/0959683614540958 SN - 0959-6836 SN - 1477-0911 VL - 24 IS - 10 SP - 1206 EP - 1215 PB - Sage Publ. CY - London ER - TY - THES A1 - Tabares Jimenez, Ximena del Carmen T1 - A palaeoecological approach to savanna dynamics and shrub encroachment in Namibia N2 - The spread of shrubs in Namibian savannas raises questions about the resilience of these ecosystems to global change. This makes it necessary to understand the past dynamics of the vegetation, since there is no consensus on whether shrub encroachment is a new phenomenon, nor on its main drivers. However, a lack of long-term vegetation datasets for the region and the scarcity of suitable palaeoecological archives, makes reconstructing past vegetation and land cover of the savannas a challenge. To help meet this challenge, this study addresses three main research questions: 1) is pollen analysis a suitable tool to reflect the vegetation change associated with shrub encroachment in savanna environments? 2) Does the current encroached landscape correspond to an alternative stable state of savanna vegetation? 3) To what extent do pollen-based quantitative vegetation reconstructions reflect changes in past land cover? The research focuses on north-central Namibia, where despite being the region most affected by shrub invasion, particularly since the 21st century, little is known about the dynamics of this phenomenon. Field-based vegetation data were compared with modern pollen data to assess their correspondence in terms of composition and diversity along precipitation and grazing intensity gradients. In addition, two sediment cores from Lake Otjikoto were analysed to reveal changes in vegetation composition that have occurred in the region over the past 170 years and their possible drivers. For this, a multiproxy approach (fossil pollen, sedimentary ancient DNA (sedaDNA), biomarkers, compound specific carbon (δ13C) and deuterium (δD) isotopes, bulk carbon isotopes (δ13Corg), grain size, geochemical properties) was applied at high taxonomic and temporal resolution. REVEALS modelling of the fossil pollen record from Lake Otjikoto was run to quantitatively reconstruct past vegetation cover. For this, we first made pollen productivity estimates (PPE) of the most relevant savanna taxa in the region using the extended R-value model and two pollen dispersal options (Gaussian plume model and Lagrangian stochastic model). The REVEALS-based vegetation reconstruction was then validated using remote sensing-based regional vegetation data. The results show that modern pollen reflects the composition of the vegetation well, but diversity less well. Interestingly, precipitation and grazing explain a significant amount of the compositional change in the pollen and vegetation spectra. The multiproxy record shows that a state change from open Combretum woodland to encroached Terminalia shrubland can occur over a century, and that the transition between states spans around 80 years and is characterized by a unique vegetation composition. This transition is supported by gradual environmental changes induced by management (i.e. broad-scale logging for the mining industry, selective grazing and reduced fire activity associated with intensified farming) and related land-use change. Derived environmental changes (i.e. reduced soil moisture, reduced grass cover, changes in species composition and competitiveness, reduced fire intensity) may have affected the resilience of Combretum open woodlands, making them more susceptible to change to an encroached state by stochastic events such as consecutive years of precipitation and drought, and by high concentrations of pCO2. We assume that the resulting encroached state was further stabilized by feedback mechanisms that favour the establishment and competitiveness of woody vegetation. The REVEALS-based quantitative estimates of plant taxa indicate the predominance of a semi-open landscape throughout the 20th century and a reduction in grass cover below 50% since the 21st century associated with the spread of encroacher woody taxa. Cover estimates show a close match with regional vegetation data, providing support for the vegetation dynamics inferred from multiproxy analyses. Reasonable PPEs were made for all woody taxa, but not for Poaceae. In conclusion, pollen analysis is a suitable tool to reconstruct past vegetation dynamics in savannas. However, because pollen cannot identify grasses beyond family level, a multiproxy approach, particularly the use of sedaDNA, is required. I was able to separate stable encroached states from mere woodland phases, and could identify drivers and speculate about related feedbacks. In addition, the REVEALS-based quantitative vegetation reconstruction clearly reflects the magnitude of the changes in the vegetation cover that occurred during the last 130 years, despite the limitations of some PPEs. This research provides new insights into pollen-vegetation relationships in savannas and highlights the importance of multiproxy approaches when reconstructing past vegetation dynamics in semi-arid environments. It also provides the first time series with sufficient taxonomic resolution to show changes in vegetation composition during shrub encroachment, as well as the first quantitative reconstruction of past land cover in the region. These results help to identify the different stages in savanna dynamics and can be used to calibrate predictive models of vegetation change, which are highly relevant to land management. N2 - Die Ausbreitung von Sträuchern in der namibischen Savanne wirft Fragen nach der Resilienz dieser Ökosysteme gegenüber globalen Veränderungen auf. Dies macht es notwendig, die Vegetationsdynamik in der Vergangenheit zu verstehen, da kein Konsens darüber besteht, ob die Verbuschung ein neues Phänomen ist oder über ihre Haupttreiber. Aufgrund des Mangels an Langzeitvegetationsdatensätzen für die Region und des Mangels an geeigneten paläoökologischen Archiven bleibt die Rekonstruktion der früheren Vegetation und der früheren Landbedeckung der Savannen eine Herausforderung. In diesem Zusammenhang befasst sich diese Studie mit drei Hauptforschungsfragen: 1) Ist Pollenanalyse ein geeignetes Instrument, um die Veränderung der Vegetation widerzuspiegeln, die mit der Verbuschung von Savannen verbunden ist? 2) Entspricht die derzeitige verbuschte Landschaft einem stabilen Zustand der Savannenvegetation? 3) Inwieweit entspricht die quantitative Rekonstruktion der Vegetation auf der Grundlage fossiler Pollendaten der früheren Vegetationsbedeckung der Savanne? Um diese Fragen zu beantworten, konzentrierte sich diese Forschung auf Nord-Zentral-Namibia, da diese Region insbesondere seit dem 21. Jahrhundert am stärksten von Verbuschung betroffen ist, über die Dynamik dieses Phänomens in der Region ist jedoch wenig bekannt. Im Rahmen dieser Studie wurden feldbasierte Vegetationsdaten mit modernen Pollendaten verglichen, um das Potenzial moderner Pollen zu bewerten, die Vegetationszusammensetzung und -vielfalt entlang von Niederschlags- und Weideintensitätsgradienten widerzuspiegeln. Zusätzlich wurden zwei Sedimentkerne aus dem Otjikoto-See analysiert, um die Veränderungen der Vegetationszusammensetzung in der Region in den letzten 170 Jahren und ihre möglichen Treiber zu dokumentieren. Hierzu wurde ein Multiproxy-Ansatz (fossiler Pollen, sedimentäre alte DNA, Biomarker, verbindungsspezifische Kohlenstoff- (δ13C) und Deuterium- (δD) Isotope, Kohlenstoff-Isotope (δ13Corg), Korngröße, geochemische Eigenschaften) mit hoher taxonomischer und zeitlicher Auflösung angewendet. Schließlich wurde der REVEALS-Ansatz auf den fossilen Pollendata des Otjikoto-Sees angewendet, um die Vegetationsbedeckung der Vergangenheit quantitativ zu rekonstruieren. Dazu wurden zunächst die Pollenproduktivitätsschätzungen (PPE) der relevantesten Savannentaxa in der Region unter Verwendung des erweiterten R-Wert-Modells und zweier Pollenausbreitungsmodelle (Gaußsches Federmodell und Lagrange-Stochastikmodell) berechnet. Die auf REVEALS basierende Vegetationsrekonstruktion wurde dann unter Verwendung von auf Fernerkundung basierenden regionalen Vegetationsdaten validiert. Die Ergebnisse zeigen, dass moderner Pollen die Zusammensetzung der Vegetation gut widerspiegelt, jedoch weniger die Diversität. Interessanterweise machen Niederschlag und Beweidung einen signifikanten, aber geringen Anteil der Änderung der Zusammensetzung in den Pollen- und Vegetationsspektren aus. Die Multiproxy-Analyse zeigt, dass ein Zustandswechsel von der offenen Combretum Baumsavanne zum Terminalia Buschland über ein Jahrhundert stattfinden kann und dass der Übergang zwischen den beiden Zuständen etwa 80 Jahre dauert und durch eine einzigartige Vegetationszusammensetzung gekennzeichnet ist. Dieser Übergang wird durch allmähliche Umweltveränderungen unterstützt, die durch das Management (z.B. großflächige Abholzung für den Bergbau sowie selektive Beweidung und verringerte Feueraktivität verbunden mit intensivierter Landwirtschaft) und damit verbundene Landnutzungsänderungen hervorgerufen werden. Abgeleitete Umweltveränderungen (z.B. verringerte Bodenfeuchtigkeit, verringerte Grasbedeckung, Änderungen der Artenzusammensetzung und Konkurrenzfähigkeit, verringerte Feuerintensität) können die Resilienz der offenen Combretum Baumsavanne beeinträchtigt haben und sie anfälliger machen, durch stochastische Ereignisse wie aufeinanderfolgende niederschlagsreiche Jahre, Dürre, und durch hohe Konzentrationen von pCO2, in einen verbuschten Zustand zu wechseln. Der daraus resultierende verbuschte Zustand wird durch Rückkopplungsmechanismen aufrechterhalten, welche die Etablierung und Konkurrenzfähigkeit der Holzvegetation begünstigen. Schließlich deuten die auf REVEALS basierenden Deckungsschätzungen auf das Vorherrschen einer halboffenen Landschaft während des gesamten 20. Jahrhunderts und eine Verringerung der Grasbedeckung unter 50% seit dem 21. Jahrhundert hin, die mit der Verbreitung von Verbuschungstaxa verbunden ist. Deckungsschätzungen zeigen eine enge Übereinstimmung mit regionalen Vegetationsdaten, wodurch die aus der Multi-Proxy-Analyse abgeleitete Vegetationsdynamik bestätigt werden kann. Die PPE-Berechnung war für alle holzigen Taxa erfolgreich, für Poaceae jedoch fehlgeschlagen. Zusammenfassend ist die Pollenanalyse ein geeignetes Instrument zur Rekonstruktion der Vegetationsdynamik in Savannen. Aufgrund der geringen taxonomischen Auflösung von Pollen zur Identifizierung von Gräsern ermöglicht ein Multiproxy-Ansatz, insbesondere die Verwendung von sedaDNA, die Unterscheidung stabiler verbuschte Zustände von bloßen Waldphasen sowie die Identifizierung von Auslösern und Treibern von Zustandsänderungen. Darüber hinaus spiegelt die auf REVEALS basierende quantitative Vegetationsrekonstruktion trotz der Einschränkungen bei der Berechnung von PPEs deutlich das Ausmaß der Veränderungen in der Vegetationsbedeckung wider, die in den letzten 130 Jahren aufgetreten sind. Diese Forschung liefert neue Einblicke in die Pollen-Vegetations-Beziehungen in Savannen und unterstreicht die Bedeutung von Multiproxy-Ansätzen zur Rekonstruktion der Vegetationsdynamik in semi-ariden Landschaften. Es bietet auch die erste Zeitreihe mit ausreichender taxonomischer Auflösung, um die Veränderungen der Vegetationszusammensetzung im Verlauf der Verbuschung sowie die erste quantitative Rekonstruktion der früheren Landbedeckung in der Region aufzuzeigen. Diese Ergebnisse können dazu beitragen, die verschiedenen Stadien der Savannendynamik besser zu identifizieren, und können auch zur Kalibrierung von Vorhersagemodellen für Vegetationsänderungen verwendet werden, die für die Landbewirtschaftung von großem Wert sind. T2 - Ein paläoökologischer Ansatz zur Savannendynamik und Verbuschung in Namibia KW - savanna ecology KW - pollen KW - sedaDNA KW - REVEALS KW - state-transition models KW - Savannen-Ökologie KW - REVEALS KW - sedimentäre alte DNA KW - Pollen KW - Pollenproduktivitätsschätzungen KW - Zustands-Übergangs-Modelle Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-492815 ER - TY - JOUR A1 - Schirrmeister, Lutz A1 - Bobrov, Anatoly A1 - Raschke, Elena A1 - Herzschuh, Ulrike A1 - Strauss, Jens A1 - Pestryakova, Luidmila Agafyevna A1 - Wetterich, Sebastian T1 - Late Holocene ice-wedge polygon dynamics in northeastern Siberian coastal lowlands JF - Arctic, antarctic, and alpine research : an interdisciplinary journal N2 - Ice-wedge polygons are common features of northeastern Siberian lowland periglacial tundra landscapes. To deduce the formation and alternation of ice-wedge polygons in the Kolyma Delta and in the Indigirka Lowland, we studied shallow cores, up to 1.3 m deep, from polygon center and rim locations. The formation of well-developed low-center polygons with elevated rims and wet centers is shown by the beginning of peat accumulation, increased organic matter contents, and changes in vegetation cover from Poaceae-, Alnus-, and Betula-dominated pollen spectra to dominating Cyperaceae and Botryoccocus presence, and Carex and Drepanocladus revolvens macro-fossils. Tecamoebae data support such a change from wetland to open-water conditions in polygon centers by changes from dominating eurybiontic and sphagnobiontic to hydrobiontic species assemblages. The peat accumulation indicates low-center polygon formation and started between 2380 +/- 30 and 1676 +/- 32 years before present (BP) in the Kolyma Delta. We recorded an opposite change from open-water to wetland conditions because of rim degradation and consecutive high-center polygon formation in the Indigirka Lowland between 2144 +/- 33 and 1632 +/- 32 years BP. The late Holocene records of polygon landscape development reveal changes in local hydrology and soil moisture. KW - Permafrost KW - cryolithology KW - radiocarbon dating KW - paleoecology KW - rhizopods KW - pollen KW - plant macro-fossils Y1 - 2018 U6 - https://doi.org/10.1080/15230430.2018.1462595 SN - 1523-0430 SN - 1938-4246 VL - 50 IS - 1 PB - Institute of Arctic and Alpine Research, University of Colorado CY - Boulder ER - TY - GEN A1 - Schirrmeister, Lutz A1 - Bobrov, Anatoly A1 - Raschke, Elena A1 - Herzschuh, Ulrike A1 - Strauss, Jens A1 - Pestryakova, Luidmila Agafyevna A1 - Wetterich, Sebastian T1 - Late Holocene ice-wedge polygon dynamics in northeastern Siberian coastal lowlands T2 - Postprints der Universität Potsdam Mathematisch-Naturwissenschaftliche Reihe N2 - Ice-wedge polygons are common features of northeastern Siberian lowland periglacial tundra landscapes. To deduce the formation and alternation of ice-wedge polygons in the Kolyma Delta and in the Indigirka Lowland, we studied shallow cores, up to 1.3 m deep, from polygon center and rim locations. The formation of well-developed low-center polygons with elevated rims and wet centers is shown by the beginning of peat accumulation, increased organic matter contents, and changes in vegetation cover from Poaceae-, Alnus-, and Betula-dominated pollen spectra to dominating Cyperaceae and Botryoccocus presence, and Carex and Drepanocladus revolvens macro-fossils. Tecamoebae data support such a change from wetland to open-water conditions in polygon centers by changes from dominating eurybiontic and sphagnobiontic to hydrobiontic species assemblages. The peat accumulation indicates low-center polygon formation and started between 2380 +/- 30 and 1676 +/- 32 years before present (BP) in the Kolyma Delta. We recorded an opposite change from open-water to wetland conditions because of rim degradation and consecutive high-center polygon formation in the Indigirka Lowland between 2144 +/- 33 and 1632 +/- 32 years BP. The late Holocene records of polygon landscape development reveal changes in local hydrology and soil moisture. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 719 KW - permafrost KW - cryolithology KW - radiocarbon dating KW - paleoecology KW - rhizopods KW - pollen KW - plant macro-fossils Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-426603 SN - 1866-8372 IS - 719 ER - TY - GEN A1 - Niemeyer, Bastian A1 - Herzschuh, Ulrike A1 - Pestryakova, Luidmila Agafyevna T1 - Vegetation and lake changes on the southern Taymyr peninsula, northern Siberia, during the last 300 years inferred from pollen and Pediastrum green algae records T2 - The Holocene N2 - Siberian arctic vegetation and lake water communities, known for their temperature dependence, are expected to be particularly impacted by recent climate change and high warming rates. However, decadal information on the nature and strength of recent vegetation change and its time lag to climate signals are rare. In this study, we present a Pb-210/Cs-137 dated pollen and Pediastrum species record from a unnamed lake in the south of the Taymyr peninsula covering the period from AD 1706 to 2011. Thirty-nine palynomorphs and 10 morphotypes of Pediastrum species were studied to assess changes in vegetation and lake conditions as probable responses to climate change. We compared the pollen record with Pediastrum species, which we consider to be important proxies of climate changes. Three pollen assemblage zones characterised by Betula nana, Alnus viridis and Larix gmelinii (1706-1808); herbs such as Cyperaceae, Artemisia or Senecio (1808-1879), and higher abundance of Larix pollen (1955-2011) are visible. Also, three Pediastrum assemblage zones show changes of aquatic conditions: higher abundances of Pediastrum boryanum var. brevicorne (1706-1802); medium abundances of P. kawraiskyi and P. integrum (1802-1840 and 1920-1980), indicating cooler conditions while less eutrophic conditions are indicated by P. boryanum, and a mainly balanced composition with only small changes of cold- and warm-adapted Pediastrum species (1965-2011). In general, compositional Pediastrum species turnover is slightly higher than that indicated by pollen data (0.54 vs 0.34 SD), but both are only minor for this treeline location. In conclusion, the relevance of differentiation of Pediastrum species is promising and can give further insights into the relationship between lakes and their surrounding vegetation transferred onto climatic conditions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 421 KW - morphotypes KW - Pediastrum KW - pollen KW - Siberia KW - treeline KW - vegetation Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-404882 VL - 25 IS - 4 ER - TY - JOUR A1 - Niemeyer, Bastian A1 - Herzschuh, Ulrike A1 - Pestryakova, Luidmila Agafyevna T1 - Vegetation and lake changes on the southern Taymyr peninsula, northern Siberia, during the last 300 years inferred from pollen and Pediastrum green algae records JF - The Holocene : an interdisciplinary journal focusing on recent environmental change N2 - Siberian arctic vegetation and lake water communities, known for their temperature dependence, are expected to be particularly impacted by recent climate change and high warming rates. However, decadal information on the nature and strength of recent vegetation change and its time lag to climate signals are rare. In this study, we present a Pb-210/Cs-137 dated pollen and Pediastrum species record from a unnamed lake in the south of the Taymyr peninsula covering the period from AD 1706 to 2011. Thirty-nine palynomorphs and 10 morphotypes of Pediastrum species were studied to assess changes in vegetation and lake conditions as probable responses to climate change. We compared the pollen record with Pediastrum species, which we consider to be important proxies of climate changes. Three pollen assemblage zones characterised by Betula nana, Alnus viridis and Larix gmelinii (1706-1808); herbs such as Cyperaceae, Artemisia or Senecio (1808-1879), and higher abundance of Larix pollen (1955-2011) are visible. Also, three Pediastrum assemblage zones show changes of aquatic conditions: higher abundances of Pediastrum boryanum var. brevicorne (1706-1802); medium abundances of P. kawraiskyi and P. integrum (1802-1840 and 1920-1980), indicating cooler conditions while less eutrophic conditions are indicated by P. boryanum, and a mainly balanced composition with only small changes of cold- and warm-adapted Pediastrum species (1965-2011). In general, compositional Pediastrum species turnover is slightly higher than that indicated by pollen data (0.54 vs 0.34 SD), but both are only minor for this treeline location. In conclusion, the relevance of differentiation of Pediastrum species is promising and can give further insights into the relationship between lakes and their surrounding vegetation transferred onto climatic conditions. KW - morphotypes KW - Pediastrum KW - pollen KW - Siberia KW - treeline KW - vegetation Y1 - 2015 U6 - https://doi.org/10.1177/0959683614565954 SN - 0959-6836 SN - 1477-0911 VL - 25 IS - 4 SP - 596 EP - 606 PB - Sage Publ. CY - London ER - TY - JOUR A1 - Niemeyer, Bastian A1 - Epp, Laura Saskia A1 - Stoof-Leichsenring, Kathleen Rosemarie A1 - Pestryakova, Luidmila Agafyevna A1 - Herzschuh, Ulrike T1 - A comparison of sedimentary DNA and pollen from lake sediments in recording vegetation composition at the Siberian treeline JF - Molecular ecology resources N2 - Reliable information on past and present vegetation is important to project future changes, especially for rapidly transitioning areas such as the boreal treeline. To study past vegetation, pollen analysis is common, while current vegetation is usually assessed by field surveys. Application of detailed sedimentary DNA (sedDNA) records has the potential to enhance our understanding of vegetation changes, but studies systematically investigating the power of this proxy are rare to date. This study compares sedDNA metabarcoding and pollen records from surface sediments of 31 lakes along a north-south gradient of increasing forest cover in northern Siberia (Taymyr peninsula) with data from field surveys in the surroundings of the lakes. sedDNA metabarcoding recorded 114 plant taxa, about half of them to species level, while pollen analyses identified 43 taxa, both exceeding the 31 taxa found by vegetation field surveys. Increasing Larix percentages from north to south were consistently recorded by all three methods and principal component analyses based on percentage data of vegetation surveys and DNA sequences separated tundra from forested sites. Comparisons of the ordinations using procrustes and protest analyses show a significant fit among all compared pairs of records. Despite similarities of sedDNA and pollen records, certain idiosyncrasies, such as high percentages of Alnus and Betula in all pollen and high percentages of Salix in all sedDNA spectra, are observable. Our results from the tundra to single-tree tundra transition zone show that sedDNA analyses perform better than pollen in recording site-specific richness (i.e., presence/absence of taxa in the vicinity of the lake) and perform as well as pollen in tracing vegetation composition. KW - environmental DNA KW - metabarcoding KW - pollen KW - Siberia KW - trnL marker KW - vegetation Y1 - 2017 U6 - https://doi.org/10.1111/1755-0998.12689 SN - 1755-098X SN - 1755-0998 VL - 17 SP - e46 EP - e62 PB - Wiley CY - Hoboken ER -